Exercise Improves Survival in Chronic Kidney Disease

Action Points

Explain to interested patients that people with chronic kidney disease, like most of the population, have a decreased risk of death if they excercise regularly.

Note that this observational study could not establish a causal relationship between increasing physical activity and improvements in survival in patients with chronic kidney disease.

Much like the rest of the population, patients with chronic kidney disease have a decreased risk of death if they exercise regularly, according to an analysis of National Health and Nutrition Examination Survey (NHANES) data.

Patients who got the recommended amount of weekly exercise were 56% less likely to die through seven years of follow-up than those who did not exercise at all (HR 0.44, 95% CI 0.33 to 0.58), according to Srinivasan Beddhu, MD, of the University of Utah in Salt Lake City, and colleagues.

Those who exercised, but at less than the recommended level of activity, were still 42% less likely to die during follow-up than sedentary patients (HR 0.58, 95% CI 0.42 to 0.79).

The findings were reported online in the Clinical Journal of the American Society of Nephrology.

Most patients with chronic kidney disease die before developing end-stage renal disease, but the current focus for clinicians is on slowing disease progression rather than reducing mortality, the researchers noted.

Still, one measure that may be helpful in improving survival in these patients is increasing exercise, they wrote.

A previous research effort, the Modification of Diet in Renal Disease (MDRD) study, suggested that the mortality benefits of physical activity might not apply to patients with chronic kidney disease.

To further explore the issue, Beddhu and his colleagues examined data from NHANES III (1988-1994), which included 15,368 participants. Of those, 5.9% had chronic kidney disease (estimated glomerular filtration rate <60 mL/min per 1.73 m2).

Based on the results of a questionnaire, the participants were divided into three groups:

Active: moderate activity at least five times a week or rigorous activity at least three times a week

Insufficiently active: not inactive, but short of recommended activity levels

Inactive

Chronic kidney disease patients were significantly more likely to be inactive than the other NHANES III participants (28% versus 13.5%, P<0.001).

After adjusting for potential confounders, participants in either one of the active groups had decreased risks of dying during follow-up, which was an average of seven years for patients with chronic kidney disease and 8.8 years for others.

The magnitudes of the benefits were similar in patients with chronic kidney disease and the other participants (P>0.3), "indicating that the associations of physical activity with mortality did not differ by the presence or absence of chronic kidney disease," the researchers said.

They said the findings likely differ from those of the MDRD study because of variation in the study designs, including different methods for assessing physical activity, and the occurrence of fewer deaths in the previous study.

The authors noted limitations of the study, including the inability to establish a causal relationship between exercise and mortality because of the observational design, possible residual confounding, and the use of self-reported information on physical activity.

The study was supported by a grant from the Dialysis Research Foundation of Utah. Beddhu is the recipient of grants from the National Institute of Diabetes and Digestive and Kidney Diseases.

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